Intestine mast cells /eosinophilic granule
cells (MCs/EGC) of the marine species Centropomus parallelus (fat snook) were first studied using
light and
electron microscopy techniques .
Mast cells are
cells from the
connective tissue found in almost all organs and
tissues of
vertebrates . In fish, they appear in greater numbers in parts of their bodies that are exposed to their
environment , such as
skin ,
gills and
intestine . The granules in fat snook's
mast cell contain a variety of substances, such as
histamine ,
heparin ,
chondroitin sulfate ,
serotonin ,
proteases and
cytokines . The present study of
intestine MCs/EGC was carried out in 20 specimens of fat snook. Samples of
tissue were fixed in Bouin
solution and in buffered
formalin . Ferric
hematoxylin -
Congo red , pH6
acridine orange , pH2.5 and pH0,5
Alcian Blue (AB),
toluidine blue , PAS, AB + PAS and
immunohistochemistry protocols were used. In the
mucosa and submucosa layers, MCs/EGCs granules with basic contents were evidenced by
Congo red staining , and with
acid contents granules were identified through
pH 2.5 and 0,5 AB, and
acridine orange . Basic and
acid contents were simultaneously evidenced using ferric
hematoxylin -
Congo red stain . Metachromasia was observed in both mucosal and submucosal
mast cells . Neutral
glycoproteins were evidenced by using PAS protocol,
glycosaminoglycan through AB and both simultaneously through AB + PAS. In
immunohistochemistry assays, MCs/EGC were positive for
tryptase ,
chymase and
serotonin . As in
mammals , the study of samples fixed in modified Karnovsky for
transmission electron microscopy evidenced that most of the MCs granules were spherical and showed varying
electron density, as described in previous
reports on other teleost fish species. The metachromasia observed and the identification of
tryptase ,
chymase and
serotonin suggest a great similarity between fat snook's MCs/EGC and those described in the
mucosa of
mammals .